In rotary drilling operations, a fluid commonly called “drilling mud” is circulated into and out of the hole being drilled. Drilling mud is used to control subsurface pressures, lubricate the drill bit, stabilize the well bore, and carry the cuttings to the surface, among other functions. In a typical drilling mud circulation system, drilling mud is circulated down a drill string, i.e. a pipe and tool configuration, directed through openings in a drill bit on the lower end of the drill pipe, and returned to the surface through the annular space between the drill string and the walls of the hole and a casing. As the drill bit grinds rocks into drill cuttings, the resulting debris, including sand, gravel, clay, and other particulate matter, is typically transported out of the hole to clean the debris prior to discarding the debris and to further separate any hydrocarbon material from the drilling mud.
It is known in the art to process the drill mud and drill cuttings mixture by directing the return drill mud mixture through shakers, screens, centrifuges, and fluidized beds to separate the cuttings from the drill mud before returning the drill mud to a storage area for reuse and to discard the drill cuttings. It is desirable, not only to remove the larger more coarse particles from the drill mud and cuttings mixture, but also to further remove as many fine solids as possible because these particles tend to interfere with drilling performance.
However, numerous deficiencies exist with respect to these known devices. Shaker screens are especially prone to clogging and wear, especially when drilling into clay. Cyclones are also prone to wear and require a significant amount of pump energy. Centrifuges, as well as shaker screens and cyclones, are generally unable to adequately separate clays from sand and gravel. These deficiencies exist with the use of such devices to separate drill cuttings from drill mud and to clean the separated cuttings, but such deficiencies also exist with the use of these devices to separate cement from sand, separate various minerals from one another, and other solid/solid or solid/fluid separations.
Moreover, while a number of other stand-alone separation devices are known, such devices are incapable of continuously separating particulate matter and continuously removing the separated particles from the separation device. Still another deficiency with such prior art devices is that they generally require the addition of a significant amount of fluid in order to separate the solid material, thereby increasing the costs of such separation.
Accordingly, there is a substantial need for a method and system that is efficient, cost effective, and environmentally safe, and that can be performed in a continuous mode to separate particulate matter based on particle size and/or density with a minimal amount of added fluid.